Prescription psychoactive drugs can help patients manage chronic or severe pain, restore emotional or behavioral balance, control sleep disorders, or fight obesity. When such prescription medications are abused, however, the consequences, including addiction, can be dangerous, even deadly. The risks associated with abuse of three classes of commonly abused prescription drugs, i.e., opioids; central nervous system (CNS) depressants, including sedatives and tranquilizers; and stimulants, are well documented.
Opioids include morphine, codeine, and related drugs such as oxycodone (Percodan and OxyContin), hydrocodone (Vicodin), and meperidine (Demerol) and are commonly prescribed to relieve pain. Taken as prescribed, opioids can be used to manage pain effectively without unwanted side effects. Chronic use of opioids can result in tolerance, which means that users must take higher doses to achieve the same effects. Long-term use also can lead to physical dependence and addiction. Withdrawal can occur when an individual discontinues use of the drugs. Withdrawal symptoms can include restlessness, muscle and bone pain, insomnia, diarrhea, vomiting, cold flashes with goose humps, and involuntary leg movements. Individuals who are addicted to opioids are more likely to overdose on the drugs, which could be fatal.
Among the most commonly prescribed CNS depressants are barbiturates, such as mephobarbital (Mebaral) and pentobarbital sodium (Nembutal), which are prescribed to treat anxiety, tension, and sleep disorders; and benzodiazepines, such as diazepam (Valium) and alprazolam (Xanax), which typically are prescribed to treat anxiety, acute stress reactions, and panic attacks. Other benzodiazepines, such as triazolam (Halcion) and estazolam (ProSom), are prescribed for short-term treatment of sleep disorders. Although the various classes of CNS depressants work differently, they all produce a beneficial drowsy or calming effect in individuals suffering from sleep disorders or anxiety. However, if one uses these drugs over a long period of time, the body will develop tolerance, and larger doses will be needed to achieve the initial effects. In addition, continued use can lead to physical dependence and, when use is reduced or stopped, withdrawal. Both barbiturates and benzodiazepines have the potential for abuse and should be used only as prescribed. As with opioids, an overdose of these drugs can be fatal.
Stimulants increase heart rate, blood pressure and metabolism, provide feelings of exhilaration and energy, and increase mental alertness. Stimulants such as methylphenidate (Ritalin) and dextroamphetamine (Adderall and Dexedrine) are prescribed for the treatment of narcolepsy, attention-deficit/hyperactivity disorder, and depression that has not responded to other treatments. They also may be used for short-term treatment of obesity. Individuals may become addicted to the sense of well-being and enhanced energy that stimulants can generate. Taking high doses of stimulants repeatedly over a short time, however, can lead to feelings of hostility or paranoia. Additionally, taking high doses of stimulants may result in dangerously high body temperatures and an irregular heartbeat.
Abuse potential of these three classes of drugs is of major concern. This is specially true for opioids and stimulants and hence they are classified by the Drug Enforcement Agency (DEA) as Schedule II drugs (substances that have a high potential for abuse with severe liability to cause psychic or physical dependence, but have some approved medical use).
Various dosage forms of psychoactive drugs for medical use are available or possible. These include capsules, tablets, transdermal patches and liquid suspensions. For example, methylphenidate (Ritalin) is available in oral, tablet and extended-release tablet dosage forms. Dextroamphetamine (Adderall) is available in immediate-release tablet and extended-release capsule dosage forms. Methylphenidate, amphetamine, fentanyl, 3-methyl fentanyl, morphine, etorphine, etc. can be incorporated into transdermal patches. A fentanyl patch (Duragesic) is already in the marketplace and a methylphenidate patch (Methypatch) is under FDA review. Liquid suspensions of drugs in immediate release and sustained release forms are also possible. A sustained release system can be formulated by using drug ion-exchange complex particles with a further coating of ethyl cellulose. The ion-exchange technology makes reliable liquid controlled-release possible for many ionic drugs, which include amphetamine, methylphenidate, hydrocodone, codeine, morphine, and the like.
These various dosage forms provide valuable medical benefits when properly taken or administered, but also have a high potential for abuse. For example, sustained release dosage forms are abused by crushing or chewing and then swallowing or snorting or by mixing or dissolving in water or the like and then injecting. Transdermal patches can be chewed to provide a quick onset via buccal, sublingual, or oral absorption of the controlled substances. In addition, a significant drug residue after normal administration of the patches is quite common. Such residue can be extracted and concentrated for abuse. Liquid suspensions can be similarly concentrated and abused.
It view of these problems, new and improved dosage forms of psychoactive drugs having decreased abuse potential are desired. Several approaches to reducing the abuse potential of dosage forms of drugs can be found in U.S. patents. These include, for example, the incorporation of an opioid antagonist into a dosage form (U.S. Pat. Nos. 4,401,672, 4,457,933, 5,162,341, 5,236,714, 6,277,384 and 6,228,863), the use of cytochrome P450 2D6 enzyme inhibitor (U.S. Pat. No. 6,124,282), and the incorporation of a water soluble/gelable material into a dosage form (U.S. Pat. No. 4,070,494). However, these approaches still are far from ideal in terms of the effectiveness of deterring someone from abusing the medication by snorting or improper oral administration.